Nguyen Giang D, Tsai Hsin-Zon, Omrani Arash A, Marangoni Tomas, Wu Meng, Rizzo Daniel J, Rodgers Griffin F, Cloke Ryan R, Durr Rebecca A, Sakai Yuki, Liou Franklin, Aikawa Andrew S, Chelikowsky James R, Louie Steven G, Fischer Felix R, Crommie Michael F
Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA.
Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA.
Nat Nanotechnol. 2017 Nov;12(11):1077-1082. doi: 10.1038/nnano.2017.155. Epub 2017 Sep 25.
The rational bottom-up synthesis of atomically defined graphene nanoribbon (GNR) heterojunctions represents an enabling technology for the design of nanoscale electronic devices. Synthetic strategies used thus far have relied on the random copolymerization of two electronically distinct molecular precursors to yield GNR heterojunctions. Here we report the fabrication and electronic characterization of atomically precise GNR heterojunctions prepared through late-stage functionalization of chevron GNRs obtained from a single precursor. Post-growth excitation of fully cyclized GNRs induces cleavage of sacrificial carbonyl groups, resulting in atomically well-defined heterojunctions within a single GNR. The GNR heterojunction structure was characterized using bond-resolved scanning tunnelling microscopy, which enables chemical bond imaging at T = 4.5 K. Scanning tunnelling spectroscopy reveals that band alignment across the heterojunction interface yields a type II heterojunction, in agreement with first-principles calculations. GNR heterojunction band realignment proceeds over a distance less than 1 nm, leading to extremely large effective fields.
原子级精确的石墨烯纳米带（GNR）异质结的合理自下而上合成是纳米级电子器件设计的一项赋能技术。迄今为止使用的合成策略依赖于两种电子性质不同的分子前体的无规共聚以产生GNR异质结。在此，我们报告了通过对由单一前体获得的人字形GNR进行后期功能化制备的原子精确GNR异质结的制造和电子表征。完全环化的GNR的生长后激发诱导牺牲羰基的裂解，从而在单个GNR内产生原子级明确的异质结。使用键分辨扫描隧道显微镜对GNR异质结结构进行了表征，该显微镜能够在T = 4.5 K下进行化学键成像。扫描隧道光谱表明，异质结界面上的能带排列产生了II型异质结，这与第一性原理计算结果一致。GNR异质结能带重新排列在小于1 nm的距离上进行，导致极大的有效场。
